530i O2 Sensors...

[Zygote55]

Hey guys...

So for the last couple months my '95 530i has had an on again/off again check engine light. The code it gives me is 1-2-2-1, which according to the repair manual means O2 Sensor #1 is bad. I had been ignoring the problem because I've been busy and broke and trying to fix my other car, but now the problem has become too big to ignore.

Two days ago I was driving on the freeway when I noticed a lack of power. Nothing major, but it was enough to make me think I had a very low tire. About 1 minute after noticing this my check engine light came on and the car began to run VERY poorly. I was flooring it in 4th and was just able to maintain 60mph for a couple minutes before I could get off the freeway and to a safe parking lot. When I got to the parking lot and stopped the engine shut off before I could turn it off, and the car would not start again. The code comes up as O2 sensor #1 again. I had a friend come pick me up so I wouldn't be late for work, and I left the car where it was.

The next day I went to autozone and bought a universal O2 sensor and replaced the driver's side O2 sensor on my BMW with the universal unit (I have no idea which sensor is #1 or #2). After replacing the sensor the car started right up and idled perfectly. I jumped in and started driving it home. The check engine light never went away, but at the time I was more concerned with just getting the car home. After about 15 miles the car was fully warmed up, and the engine began to really struggle again. I was forced to pull over to the side of the road where the engine promptly shut off and would not start again. I waited about 30 minutes for it to cool down and was able to drive it easily the remaining 5 miles home. When I got home it was still running fine, so I shut it off and tried to start it again....wouldn't start.

I left it for the night and came back to it this morning. It wouldn't start. I swapped the two O2 sensors on the car hoping if I had replaced the wrong one I could at least get a different CEL code by swapping them. Needless to say, same code, same problem, car won't start 90% of the time, and when it does start it'll only run for a few seconds before shutting off.

Any help would be greatly appreciated, especially if anybody can tell me which O2 sensor (driver's side or passenger side) is #1.

Thanks

-Keith

[Jeff in MN]

Hey guys...

So for the last couple months my '95 530i has had an on again/off again check engine light. The code it gives me is 1-2-2-1, which according to the repair manual means O2 Sensor #1 is bad. I had been ignoring the problem because I've been busy and broke and trying to fix my other car, but now the problem has become too big to ignore.

Two days ago I was driving on the freeway when I noticed a lack of power. Nothing major, but it was enough to make me think I had a very low tire. About 1 minute after noticing this my check engine light came on and the car began to run VERY poorly. I was flooring it in 4th and was just able to maintain 60mph for a couple minutes before I could get off the freeway and to a safe parking lot. When I got to the parking lot and stopped the engine shut off before I could turn it off, and the car would not start again. The code comes up as O2 sensor #1 again. I had a friend come pick me up so I wouldn't be late for work, and I left the car where it was.

The next day I went to autozone and bought a universal O2 sensor and replaced the driver's side O2 sensor on my BMW with the universal unit (I have no idea which sensor is #1 or #2). After replacing the sensor the car started right up and idled perfectly. I jumped in and started driving it home. The check engine light never went away, but at the time I was more concerned with just getting the car home. After about 15 miles the car was fully warmed up, and the engine began to really struggle again. I was forced to pull over to the side of the road where the engine promptly shut off and would not start again. I waited about 30 minutes for it to cool down and was able to drive it easily the remaining 5 miles home. When I got home it was still running fine, so I shut it off and tried to start it again....wouldn't start.

I left it for the night and came back to it this morning. It wouldn't start. I swapped the two O2 sensors on the car hoping if I had replaced the wrong one I could at least get a different CEL code by swapping them. Needless to say, same code, same problem, car won't start 90% of the time, and when it does start it'll only run for a few seconds before shutting off.

Any help would be greatly appreciated, especially if anybody can tell me which O2 sensor (driver's side or passenger side) is #1.

Thanks

-Keith

First off, I am pretty sure the passenger side is bank #1. That's the way it is with the 4.4L v8.
Next, On mine, I checked my codes, but missed the bad 02 sensor and ran that way for 2-3 months. fuel economy was slowly decreasing, but I attributed it to winter weather. Now I am to the point where if I go above 3000 rpm I throw misfire codes and the engine shuts down cylinders and I am in limp mode until I stop and reset. (Lack of power and runs crappy like your did.)
Bottom line, I think I screwed up my passenger side cat by running so long with bad o2 sensor and am throwing the misfire codes due to high back pressure. She runs fine if I keep it under 2500 rpms.

I plan to borescope my cat this weekend to see if it is really toasted.

good luck, and I'll let you know what I find.

Jeff.

[Zygote55]

Thanks Jeff.

First off, I am pretty sure the passenger side is bank #1. That's the way it is with the 4.4L v8.
Next, On mine, I checked my codes, but missed the bad 02 sensor and ran that way for 2-3 months. fuel economy was slowly decreasing, but I attributed it to winter weather. Now I am to the point where if I go above 3000 rpm I throw misfire codes and the engine shuts down cylinders and I am in limp mode until I stop and reset. (Lack of power and runs crappy like your did.)
Bottom line, I think I screwed up my passenger side cat by running so long with bad o2 sensor and am throwing the misfire codes due to high back pressure. She runs fine if I keep it under 2500 rpms.

I plan to borescope my cat this weekend to see if it is really toasted.

good luck, and I'll let you know what I find.

Jeff.

[Zygote55]

I've replaced both O2 sensors now and the problem has, if anything, become worse. The car now will not start unless I spray carb cleaner into the intake, and then it'll only run for a second or two. Could my problem have been a failing fuel pump that has now failed? Why would that throw an O2 sensor code?

[Dave M]

I've replaced both O2 sensors now and the problem has, if anything, become worse. The car now will not start unless I spray carb cleaner into the intake, and then it'll only run for a second or two. Could my problem have been a failing fuel pump that has now failed? Why would that throw an O2 sensor code?

OBC codes should be taken with a grain of salt. I've had a TPS code thrown for something unrelated and others here have had the 1221 code thrown in response to non-O2 sensor faults.

Anyhow, have you tested the fuel pressure? Having an engine spark to life when you toss carb cleaner into would certainly have me testing the pressure and pump power source.

Dave M

[Dave M]

Thanks for the response, Dave.

How do I check the fuel pressure?

1) get a Bentley, you won't regret it
2) do a search as I'm sure they are other posts on here somewhere

To give you an idea, here are my super condensed coles notes:

-First, you'll need a pressure tester. They're inexpensive and very good to have around.

-Relieve the system pressure. Easiest way is to pull the fuel pump relay, start the engine and let it die.

-The fuel 'outlet' or engine feed line is the hose on the left in the pic below. Tap into that one with the pressure tester.



-In order to run the pump without turning the key (once the pressure tester in hooked up), you can make a cheap little switch which bypasses the relay (see below)





M60 and M50 are supposed to be 51 psi (+- ~1 psi)

Its that easy.

Dave M

[Zygote55]

I've replaced both O2 sensors now and the problem has, if anything, become worse. The car now will not start unless I spray carb cleaner into the intake, and then it'll only run for a second or two. Could my problem have been a failing fuel pump that has now failed? Why would that throw an O2 sensor code?

[Zygote55]

Thanks for the response, Dave.

How do I check the fuel pressure?

OBC codes should be taken with a grain of salt. I've had a TPS code thrown for something unrelated and others here have had the 1221 code thrown in response to non-O2 sensor faults.

Anyhow, have you tested the fuel pressure? Having an engine spark to life when you toss carb cleaner into would certainly have me testing the pressure and pump power source.

Dave M

[632 Regal]

you will need to setup a test "T" and guage at the rear of the fuel rail

Thanks for the response, Dave.

How do I check the fuel pressure?

[artguy]

When I recently had my fuel pump failure I got the 1221 and 1222 fault codes for the O2 sensors. Had nothing to do with them.